The invention relates to a method for creating and/or optimizing a cam-disk function for controlling a moving machine element of a numerically controlled production machine or the like in the operating time system of the machine, and to a corresponding controller for such a machine.
Curves for controlling machine elements of production machines such as packaging machines, textile machines and the like are conventionally created outside the controller on a separate computer system, or prepared profiles are called up, or the latter are programmed on line via points or simple polynomial functions. When being created externally, the curves are created on a tool and loaded into the controller of these machines, for example as a memory-intensive interpolation point table. In the case of online creation, lists of points are created, prepared profiles are used, or polygons are created via simple polynomial functions.
A disadvantage of such a mode of procedure now resides, firstly, in that no substantial changes to these cam-disk functions can be undertaken in the operating time system of the machine controller. Rather, there is a need for renewed external creation taking account of desired changes on the separate computer system before a transfer into the controller of the production machine is then performed anew. Secondly, it has only been possible so far to create simple prepared profiles or polygons in the controller.
The machine manufacturer equips his production machine with a permanently prescribed functionality which the user can parameterize, or which can be adapted to the production process via appropriate algorithms implemented by the machine manufacturer. An additional computer is required by the machine manufacturer to create these machine programs. The consequence of this is that a machine manufacturer also generally requires an external additional computer in order to adapt or to expand the functionality of a production machine. In particular, so far there has been lacking the possibility of creating or optimizing flexible, top-quality cam-disk functions prescribing the movement of an element of the production machine, on the machine itself.
This limits the flexibility in an undesirable way, and prevents the online creation of top-quality, combined cam-disk functions.
It is therefore the object of the present invention to enable the programming and optimizing of top-quality, combined cam-disk functions via the user program.
This object is achieved according to the present invention by defining individual sections of the movement of machine elements by segments and/or points and interpolating between successive movement sections according to a prescribable interpolation rule. Instructions for inserting segments and points and for prescribing interpolation rules in relation to operating time are provided. Moreover, the programming and optimizing steps are carried out by the machine controller.
It has proved to be advantageous both for the method and for the controller according to the invention when segments are prescribed by a combination of a polynomial and a trigonometric component.
A combination of a polynomial having a polynomial degree of at least six and a sinusoidal function has proved to be particularly favorable in this case as a trigonometric component for defining segments.
Further advantageous refinements of the invention make use of linear connections or cubic splines or Bezier splines as interpolation rules for connection between consecutive movement sections. Such splines are assembled in a piecewise fashion from polynomials.
In order to be able to use the laws of motion, present in normal form, of the VDI standard 2143, the polynomial segments are stored in normal form in a generally valid fashion, and supplementary parameters referring to the respective actual extension for both axial coordinates are allocated.
It has proved, furthermore, to be favorable when the response at the edges of the cam-disk function is prescribed via criteria referring to the continuity of the position and/or the speed and/or the acceleration of the machine element.
According to a further advantageous refinement, scaling ranges and associated scaling factors for these ranges can be prescribed directly in the user program. The scaling ranges can correspond to the segment definitions, but need not do so.
When the parameters for defining the cam-disk function are derived directly from a production process for the machine, a process-adaptive cam-disk generation can be achieved through the invention.
In order to be able to define new curves, in a further advantageous design of the invention, an existing cam-disk function can be reset in the operating time system for the purpose of preparing a new definition of a cam-disk function.
A curve generated or optimized in this way according to the invention is present as a mapping in the memory of the controller and, according to a further advantageous refinement, can be used for a synchronous operation by virtue of the fact that in order to control the moving machine element, a slave shaft thereof follows an assigned main shaft of the machine element in accordance with the defined cam-disk function.
Thus, the invention can be used to reduce substantially the memory location requirement in the controller for application programs and user data by comparison with conventionally stored, copious tables. Moreover, the flexibility of a production machine equipped with the invention is decisively improved in that the functionality at the machine itself can be varied or enhanced. This additionally increases the economic efficiency of the machine.